jones



- B. w. JONES. SYSTEM OF CONTROL FOR ELECTRIQMOTORS.

'l\PPLlCl-\TH)N FILED MAYZS. 1916- Patented June 10, 1919.

Inventor m Has ffttorneg.

1 Schenectady,

UNITED STATES PATENT orricrz.

BENJAMIN W. JONES, OF SCHE-NECTADY, NEW YORK, ASSIGNOR T0 GENERALELECTRIC b COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF CONTROL FOR ELECTRIC MOTOR To aZZ whom it may concern:

Be it known that I, BENJAMIN W. JONES, a citizen of the United States,residing at county of Schenectady, State of New York, have invented acertain new and useful System of Control for Electric Motors, of whichthe following is a specification.

My invention relates to the control of hoists and the like, and has forits object the provision of means whereby the hoist may be started,stopped and generally controlled in a safe and effective manner.

My invention is particularly applicable to the control of an electricmotor which drives a load, such as a hoist, in two directions, and itprovides means for manually and automatically controlling the motor sothat accidents due to over-travel may be avoided.

It is customary to provide some means such as limit switches which willautomatically denergize theelectric driving .motor and apply a brake tobring the hoist to rest when the hoist passes one of its predeterminedlimits of travel. p

In the case of hoists and especially of the largersizes it iscustomaryto provide a circuit breaking switch which cuts off the motor from theline when either limit switch is operated. It is also desirable to slowdown the hoist before it reaches a limit switch so as to reduce the overtravel and makethe point at which the hoist will stop more certain. Oneof the objects of my in vention is to provide means whereby ,after thehoist has been slowed down, theflimit mg the control away from thecontrolle In order to regain control, the operator must operate aseparate-switch which permits the hoist to be returned but not movedforward. When the hoist has beenreturned past the point atvwhich thelimit switch o'perated, 'th at both directions of travel is restored.

' In-one form of my invention, ;I employ two. limiting devices, onealimit switch directly geared to the motor through the hoisting drums,hereinafter called a geared limit switch, and another set of limitswitches in the path; of travel of the hoistmotor and is, when it isreturned within the normal limits of travel, full control for ..vices incase the Specification of Letters Patent. Patented June 10 1919,Application filed May 26, 1916. Serial No. 100,118.

ing buckets, hereinafter called track limit switches. Manually operatedswitches in the control circuit cooperate with the master controller,the motor reversing switches, the electro-magnetically actuated brakefor the hoist, the geared limit switch and the track limit switches tothe hoist from dangers which would be pres ent if full control of themotor by means of the controller could be had when the hoist was pasteither one of its limits. I also provide means for retarding the speedof the hoisting motor by automatically inserting a controllingresistance in the motor circuit before the limit of travel has beenreached, with the further provision that the control of this resistanceis restored to the master controller when it is desired to return thehoist to the safe limits of travel,

Referring to the drawing, the single figure of which shows oneembodiment of my invention, the polyphase induction motor '1 isconnected to the supply circuit 2, through the oil switcl 3 and througheither one of the electromagnetically actuated reversing switches 4 or 5depending upon the direction of travel of the hoist desired. The motor 1is directly and 7 of shown for a balanced hoist which I have purpose ofillustration, and directly geared to the hoisting drums is the protectthe workmen and geared to the hoisting drums 6 9, and the drum 7 has ahoisting bucket 10 connected to it in a similar manner; the arrangementbeing such that when the bucket 9 is being raised the bucket 10 is beingsimultaneously lowered, and vice versa.

In the path of travel of the bucket 9 is a track limit switch 11 and inthe path of travel of the bucket 10 is a track limit switch 12, providedas additional protective degeared limit switch 8 should fail to operate.Associated with the hoisting drums is an electromagnetically actuatedfriction brake 13 which exerts a holding friction on the drum shaft whenfor anv .reason the electromagnet 14 is deenergized.

the segment ,magnet coil 16, the segments 30 and 31 of net coil 16, itis ci rcuit controlled by a hand operated switch lo. The no-volta'gerelay 16 has two switch members 17 and 18 which open the circuit to allthe controlling devices in case the current should fail or the hoist runpast one of its limits of tra el. The reversible master controller 19has two operative positions for each direction of rotation and alsohas'a contact segment 20 at its neutral or ofi' position. Each of thereversing switches -11 and 5 has mechanically connected thereto anelectrical interlock which is adapted to close a circuit through one setof contacts when its respective reversin switch is in the openposit-ion, and through another set or contacts when in the closedposition. Associated with these reversing switches is a pivotedmechanical interlock 21 which me chanically prevents both switches beingclosed at the same time. The no-voltage release magnet 22 has inoperative relation thereto a biased pivoted detent 23 which maintainsthe oil switch 3 in a. closed position against its bias to the openposition when the magnet 22 isenergized. The triple pole double throwprotective switches 24 and 25 are connected in the control circuits fora purpose to be hereinafter fully disclosed. The means for varying thespeed of the motor comprise resistances 26 and 27 connected in the rotorcircuit and controlled by electromagnetically actuated switches 28 and2t The no-voltage relay 16, and no-voltage release magnet 22 are inmultiple so that in case of failure of current or in case one of thesupply circuits to these magnets is opened, the switches 17 and 18 areopened, the oil switch 3 is opened and the reversing switch 4C or 5which had been closed is opened. The opening of the switch 18deenergizes thebrake coil 11 and the brake 13 exerts a braking pressureon the drum shaft to stop the hoist. The switch members 17 and 18,oilvswi-tch 3, reversing switch 4 or 5 and the resistance controllinswitches 28 and 29 will all be automatically opened in case the hoistruns past one of its predetermined limits.

The operation of my lows':' I

' Assho'wn in the drawing, the control circuits and the motor aredeenergized, Closin the switch 15 energizes the no-voltage re ay magnet16, the circuit 'being through 20 of the master controller, the

device is as folthe geared limit switch 8, through the track limitswitches 11 and 12 to the other side of the control circuit. Since theno-voltage release magnet 22 is in multiple with the maglikewiscenergized through the same circuit. Energization of the magnet 16 causesswitch members 17 and 18 to close, the switch member 17 closing amaintaining circuit for themagnet 16 and the The switch 15, the switches17 and 18, and

the oil switch being closed, he would turn the master controller 19 tothe first operative position a, making an energizing circuit for thecoil of the reversing switch 5 through the switch 17, the mastercontroller 19, the lower interlock contacts 32 and of reversing switch1, coil of reversing switch 5, through the right blade of switch 25,contacts 3st and 31 ot' the geared limit switch 8 and the track limitswitches 11 and 12 to the other side of the control circuit. This willclose the motor circuit through'the resistances 26 and 27 and the motorwould now run at a low speed due to the resistances in its rotorcircuit. In order to cause the motor to run at full speed, the mastercontroller is moved to its second operative position Z), completing anenergizing circuit for the coil of resistance controlling switch 28,through the switch 17, upper contacts of the master controller, upperinterlock contacts 35 and 36 of reversing switch 5, segments 37 and 38of geared limit switch 8, coil of switch 28, lower contacts oi mastercontroller, and the track limit swit hes 11 and 12 to the other side ofthe co ol circuit. The coil of switch 29 is all at the same timeenergized through the switch :mcmber 17, coilof switch 29, lov

ments of master controller 19, through limit switches 11 and 12 to theother of the control circuit. Upon the closin switches 28 and 29. theresistances 26 and 27 are short circuitcd and the motor runs at fullspeed.

If the operator should now desire to reverse the motor while the hoistis still within its predetermined limits of travel he would turn themaster controller to the off positionfdkanergizing'the reversing switch5 and opening the motor circuit. the master controller to the firstposition a. to the right he would energize the coil of By turning movingthe controller to the second position b energizing and closing thereslstanceshort.

circuiting switches 28 and 29. The circuit "for the coil of switch 28 isthrough the switch 17, upper contacts of the master con troller 19,lower interlock contacts 39 and 1S oircrersing switch 5, upper interlockcontacts %1 and 12 of reversing switch 4, seg ments 43 and 38 of thegeared limit switch, lower contacts of the master controller and tracklimit switches 11 and 12 to the other side of the control circuit. Thecircuit for coil of switch 29 is the same as for the other direction ofrotation, except for the changes caused by the movement of the mastercontroller to the right.

it the operator should now continue operating the motor 1 to raisebucket 9 and lower the bucket 10, shortly before he reached the limit oftravel the segment 43 would separate from its corresponding contact,denergizing the coil of resistance controlling switch 28, inserting theresistance 26 in the rotor circuit of the motor, decreasing the motorspeed. If the motor should continue to operate the hoist in this samedirection, the bucket 9 will reach its upper limit of travel,deenergizing the control circuits at the track limit switch 11 and alsoat the segments 30 and d4 of the geared limit switch 8. This will deenerize no-voltage relay 16, the novoltage release magnet 22, the 'coil ofreversing switch 4, the coil 14 of the brake 13 and the coil ofresistance controlling switch 29. The corresponding switches will open,deenergizingthe motor and the control circuits, the brake will beapplied to bring the hoist to rest and the resistance 27 will also be included in the rotor circuit of the motor.

Because of the inertia of the moving parts the hoist necessarily runs acertaindistance beyond the limits determined by the limit switches andit is necessary to provide some means by which the operator may safelyreturn the hoist to its proper limits of travel. If the mastercontroller 19 is moved to the off position, the no-voltagefelay 16 willnot be energized as was the case when the hoist was operating within itsproper limits of travel, since the circuit. for this relay is open atthe contact 30 of the geared limit switch and the track limit switch 11.Neither can the no-voltage release magnet and the brake magnet 14 beenergized because they are controlled by the switch members 17 and 18 ofthe 'no-voltage relay 16. The operator is in this'way prevented fromenergizing the motor'to run in either direction, and he can onlyenergize the motor to return by throwing the switch 24 to the right. Theno-voltage relay 16 may be energized if the master controller 19 is inthe off position, the circuit being through the contact 20 of the mastercontroller, the coil ii"). the middle blade of the switch 24:, segments3%; and 31 of the geared limit switch, the right blade of switch 24,track limit switch 12 to the other side of the control circuit. Theswitches 17 and 18 are thus causedto close energizing the no-voltagerclease magnet 22 and the brake coil releasing the brake 13. From thisit can be seen that by moving the switch 24- to the right position thetrack limit switch 11 has been short circuited and the geared limitswitch 8 has been rendered inefiective to deenergize the motor when thebucket 9 is beyond its upper limit of travel, and the control of themotor is independent of the limit switch 11 and that part of the gearedlimit switch 8 which protects the hoist when raising the bllCntU 9. Bymoving the master controller 19 to the first position to the right thecoil of reversing switch 5 may be energized, this time through the rightblade of switch 25, segments 34 and 31 of the geared limit switch 8, theright blade of switch 24, the track limit switch 12 to the other side ofthe control circuit. The resistances 26 and 27 in the rotor circuit areshort circuited when the master controller 29 is moved to the sec ondposition in the same manner as p re viously explained.

The operator may continue to lower the bucket 9, and raise the bucket10, buthe cannot reverse the motor for operation in the other directionby simply reversing the master controller 19 as he was able to do pre-'viously when he was operating the hoist" within its proper limits oftravel, because the circuit to the coil of reversing switch '4 has beenopened by the movement of the switch 2 I to the right position. If hehas returned the hoist to within its proper limits of travel he mayreverse the motorby first moving the controller to the oil position andthen throwing the switch 24 to the left position. He may then operate"the hoist within the proper limits of travel 111 the same manner asheretoforeexplained. if, however, the operator should attempt "toreverse the motor before the bucket 9 had returned past itspredetermined upper limits of travel While the hoist proper limits, hewot kl b closing the .circuit co-the coil of reversing switch 4;, as thecircuittothis coil would havejbeeuqopened by the movement of the switchera) the right. He could not complete the circuit for the coil of thisreversing switch't by moving the switch at to its left hand position,because that would deenergize the no-voltage relay 16, the no-voltagerelease magnet 22, the brake magnet 14 and open the oil switch 3 andapply the brake 13, as the control circuit would be open'at track limitswitch 11 and segments 30 and 44c of the geared limit switch.

, From this it can be seen that the operator can in no case render thelimiting means ineflective so as to return the hoist to itspredetermined limits 1 of travel, and then,

is returning to its;

Qprevented from;

man

an case he should thereafter run the -hoist beyond either one of itslimits.

ill)

- by Letters Patent of the Uni-ted States, is p In case the operatorshould run the hoist x15 beyond the other limit of travel, that is, whenthe bucket 10 had passed its upper limit', the geared limit. switch atthe contacts 30 and 3% and the track limit switch 12 will denergize thecontrol circuits and the motor and apply the brake. The operation ofreturning the hoist to its proper limits of travel is substantially thesame as that when the bucket 9 had passed its upper limit except that inthis case the switch 25 must be thrown to its left end position. Theprotective features above outlined are the same in this case aspreviously explained in connection with the protective features when thebucket 9 had passed its predetermined limit of travel, as will bereadily understood.

In accordance with the provisions of the patent statutes, 1 havedescribed the principle of operation of my invention, to with theapparatus which I now co l to represent the 'best embodiment thereof,

but I desire to have it understood that the apparatus shown is onlyillustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure 1.. In combination with a hoistor the like, an electric motor for operating it in two directions and areversing controller therefor, of a limit switch at each limit oftravel,

' means for opening the motor circuit and rendering the controllerinoperative to control the motor for operation ineither direction uponthe operation of either of said limit switches and means whereby controlis restored to the controller to return the hoist beyond the point wherethe limit switch operated after which full control is restored to thecontroller.

2. In combination with a hoist or the like,

an electric motor for operating it in two directions, and a reversingcontroller therefor, of a limit switch at each limit of travel, anelectro-magnetically controlled main switch for opening the motorcircuit upon the operation of either of said limit switches, connectionswhereby the operation of either of said limit switches renders thecontroller inoperative to control the motor for operation in eitherdirection, and means whereby a control circuit for the main switch isestablished independently of the limit switches to return the hoistbeyond the point where the limit switch was operated after which fullcontrol of the motor is restored to the controller..

3. In combination'with a hoist or the like, an electric motor foroperating it in two directions and a reversingcontroller therefor, of alimit switch at each limit of travel, an electro magnetically controlledmain switch for opening the motor circuit UPOT the operation of eitherof said limit switches, connections whereby the operation of eitherlimit switch renders the controller inoperative to control the motor foroperation in either direction, and means inde pendent of the controllerwhereby a control circuit for the main switch is established through thecontroller to return the hoist beyond the point where the limit switchoperated after which full control of the motor is restored to thecontroller.

4. The combination with a hoist or the like, an electric motor foroperating it in two directions and a reversing controller therefor, of aswitch operated to slow down the motor at a predetermined point in eachlimit of travel, means for opening the motor circuit and rendering thecontrollerinoperatire to control the motor after it has slowed down andupon the operation of either of said limit switches and means wherebycontrol is restored to the controller to return the hoist beyond thepoint where the limit switch operated after which full control isrestored to the controller through the limit switches and slow downswitch.

5. The combination with a hoist or the like, an electric motor foroperating it in two directions and a reversing controller therefor, ofalswitch operated to slow down the motor at aipredetermined point ineach direction of t 'avel, a limit switch at each limit of travel, meansfor opening the motor circuit and rendering the controller inopera tiveto control the motor after it has slowed down and'upon the operation ofeither of said limit switches and means whereby control is restored tothe controller to return the hoist at full speed beyond the point wherethe limit switch operated after which full control is restored to thecontroller through the limit switches and slow down switch.

6. The combination with a hoist or the -like, an electric motor foroperating it in two directions and a reversing controller down and uponlmit s'wltches, and manually operated the 1 the limit. switch cont1 -o1is restored operated after which fall own switch. a ciroult throughthecontroller In witness whereof, I have hereunto set Independent of thehmit switches and with my hand this 25th day of May, 1916. theslow.dow11 ;switch ineffective whereby 7+ BENJAMIN W. JONES.

